1. Field of the Invention:
The present invention relates to an injection molding apparatus and, more particularly, to an injection molding apparatus which is equipped with a magnetic coil for anisotropically magnetizing a plastic magnet.
2. Description of the Prior Art:
According to the prior art, a plastic magnet has resorted to injection molding means, for example, for injecting a synthetic resin material, which is admixed with powders of a magnetic material (such as barium ferrite, strontium carbonate ferrite or a rare earth element, e.g., cobalt), into the cavity of a mold and for anisotropically magnetizing the synthetic resin material injected with the use of a magnetic coil which is either fixedly disposed outside of or mounted in the aforementioned mold. In this case, such a large-sized magnetic coil as can generate a strong magnetic field (e.g., at 12,000 Oe) in the cavity of the mold is required for making the moldings sufficiently anisotropic. According to the means of that kind, i.e., the injection molding means having the large-sized magnetic coil fixedly disposed, however, that magnetic coil causes obstruction, either when the mold is to be opened so as to take out the moldings or when the mold is to be attached or detached and confirmed, thereby to raise a working problem. According to the injection molding means having the magnetic coil mounted in the mold, on the other hand, it is difficult to incorporate the coil having such a large size as is sufficient for anisotropy.